WO2010072893A1 - Estimation de variance de bruit pour réception en diversité - Google Patents

Estimation de variance de bruit pour réception en diversité Download PDF

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Publication number
WO2010072893A1
WO2010072893A1 PCT/FI2009/051014 FI2009051014W WO2010072893A1 WO 2010072893 A1 WO2010072893 A1 WO 2010072893A1 FI 2009051014 W FI2009051014 W FI 2009051014W WO 2010072893 A1 WO2010072893 A1 WO 2010072893A1
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Prior art keywords
signal
diversity branch
received
diversity
noise variance
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Honglei Miao
Risto Juhani Paatelma
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Nokia Inc
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Nokia Inc
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/08—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station
    • H04B7/0837—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station using pre-detection combining
    • H04B7/0842—Weighted combining
    • H04B7/0848—Joint weighting
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00—Baseband systems
    • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
    • H04L25/0202—Channel estimation
    • H04L25/0212—Channel estimation of impulse response
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00—Baseband systems
    • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
    • H04L25/0202—Channel estimation
    • H04L25/024—Channel estimation channel estimation algorithms
    • H04L25/0256—Channel estimation using minimum mean square error criteria
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00—Baseband systems
    • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
    • H04L25/03—Shaping networks in transmitter or receiver, e.g. adaptive shaping networks
    • H04L25/03006—Arrangements for removing intersymbol interference
    • H04L25/03178—Arrangements involving sequence estimation techniques
    • H04L25/03248—Arrangements for operating in conjunction with other apparatus
    • H04L25/03292—Arrangements for operating in conjunction with other apparatus with channel estimation circuitry
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/08—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station
    • H04B7/0837—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station using pre-detection combining
    • H04B7/0842—Weighted combining
    • H04B7/0845—Weighted combining per branch equalization, e.g. by an FIR-filter or RAKE receiver per antenna branch
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/08—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station
    • H04B7/0837—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station using pre-detection combining
    • H04B7/0842—Weighted combining
    • H04B7/0848—Joint weighting
    • H04B7/0854—Joint weighting using error minimizing algorithms, e.g. minimum mean squared error [MMSE], "cross-correlation" or matrix inversion
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/08—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station
    • H04B7/0868—Hybrid systems, i.e. switching and combining
    • H04B7/0874—Hybrid systems, i.e. switching and combining using subgroups of receive antennas
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00—Baseband systems
    • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
    • H04L25/03—Shaping networks in transmitter or receiver, e.g. adaptive shaping networks
    • H04L25/03006—Arrangements for removing intersymbol interference
    • H04L2025/0335—Arrangements for removing intersymbol interference characterised by the type of transmission
    • H04L2025/03426—Arrangements for removing intersymbol interference characterised by the type of transmission transmission using multiple-input and multiple-output channels
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00—Baseband systems
    • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
    • H04L25/0202—Channel estimation
    • H04L25/0224—Channel estimation using sounding signals
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00—Baseband systems
    • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
    • H04L25/03—Shaping networks in transmitter or receiver, e.g. adaptive shaping networks
    • H04L25/03006—Arrangements for removing intersymbol interference
    • H04L25/03012—Arrangements for removing intersymbol interference operating in the time domain
    • H04L25/03019—Arrangements for removing intersymbol interference operating in the time domain adaptive, i.e. capable of adjustment during data reception
    • H04L25/03038—Arrangements for removing intersymbol interference operating in the time domain adaptive, i.e. capable of adjustment during data reception with a non-recursive structure

Definitions

  • the exemplary and non-limiting embodiments of this invention relate generally to wireless communication systems, methods, devices and computer programs and, more specifically, relate to processing a receive-diversity signal.
  • the receiver which employs the equalizer and receiver diversity is termed a type 3 receiver according to the defining specifications (e.g., 3GPP TS25.101 , "User equipment (LJE) radio transmission and reception (FDD) (release 8)", V8.2.0 2008- 03).
  • 3GPP TS25.101 "User equipment (LJE) radio transmission and reception (FDD) (release 8)", V8.2.0 2008- 03).
  • LMMSE linear minimum mean squared error
  • the complexity of the MMSE equalizer may be high (mainly such high complexity could be due to the required matrix inversion).
  • a paper by Jianzhong Zhang, Tejas Bhatt and Giridhar Mandyam entitled “Efficient linear equalization for high data rate downlink CDMA signalling" (proceeding of IEEE 37 th Asilomar conference 2003, vol.
  • the FFT based MMSE equalizer can be straightforwardly extended to the receive diversity case given the assumption that the noise variances at two receive branches are equal.
  • the geometry values, or signal to noise ratios, associated with two receive branches can also be very different.
  • What is needed in the art is a receiver and method for receiving diversity signals that has reasonable computational complexity and that exploits the difference in noise variation at the different receive diversity branches. For example, it would be advantageous to have a receiver that does not require correlation matrix inversion. As another example, it would be advantageous to have a receiver that does not assume, when processing a received signal on two or more receive branches, that noise variation across the diversity receive branches is always the same regardless of actual noise conditions.
  • a method comprising: determining a first noise variance for a signal received on a first diversity branch; determining by the apparatus a second noise variance for a signal received on a second diversity branch; scaling the signal received on the second diversity branch as a function of a ratio of the first noise variance and the second noise variance; and estimating a received signal by combining the signal on the first diversity branch with the scaled signal on the second diversity branch.
  • a memory storing a program of computer readable instructions that when executed by at least one processor result in actions.
  • the actions comprise: determining a first noise variance for a signal received on a first diversity branch of a receiver; determining a second noise variance for a signal received on a second diversity branch of the receiver; scaling the signal received on the second diversity branch as a function of a ratio of the first noise variance and the second noise variance; and estimating a received signal by combining the signal on the first diversity branch with the scaled signal on the second diversity branch.
  • an apparatus comprising a memory storing a program of computer readable instructions; and at least one processor.
  • the at least one processor is configured, with the memory, to: determine a first noise variance for a signal received on a first diversity branch of the apparatus; determine a second noise variance for a signal received on a second diversity branch of the apparatus; scale the signal received on the second diversity branch as a function of a ratio of the first noise variance and the second noise variance; and estimate a received signal by combining the signal on the first diversity branch with the scaled signal on the second diversity branch.
  • an apparatus comprising first determining means; second determining means; scaling means; and estimating means.
  • the first determining means is for determining noise variance for a signal on a first diversity branch of a receiver.
  • the second determining means is for determining noise variance for a signal on a second diversity branch of the receiver.
  • the scaling means is for scaling the signal on the second diversity branch as a function of a ratio of the first noise variance and the second noise variance.
  • the estimating means is for estimating a received signal by combining the signal on the first diversity branch with the scaled signal on the second diversity branch.
  • Figure 1 is a schematic block diagram of a Type 3 receiver using noise variance and pilot Ec/lor estimation according to an exemplary embodiment of the invention.
  • Figure 2A shows a simplified block diagram of various electronic devices (such as for example the receiver of Figure 1 ) that are suitable for use in practicing the exemplary embodiments of this invention.
  • Figure 2B shows a more particularized block diagram of a user equipment such as that shown at Figure 2A.
  • Figure 3 is a graph of throughput of the HSDPA receiver with receive diversity comparing an exemplary embodiment of the invention against a legacy solution which assumes the same noise variance at both receive branches, where gain on the first branch is 10 dB and gain on the second branch is 1 dB.
  • Figure 4 is similar to Figure 3 but where gain on the second branch is 7 dB.
  • Figure 5 is similar to Figure 3 but where gain on both the first and second branches is 10 dB.
  • Figure 6 is a logic flow diagram that illustrates the operation of a method, and a result of execution of computer program instructions embodied on a computer readable memory, in accordance with an exemplary embodiment of this invention.
  • a process for noise variance estimation, which are the necessary information for the design of the LMMSE equalizer.
  • Such an equalizer may be employed in a particular embodiment within a HSDPA receiver with two receive branches. While such a use is the context of the description below, the HSDPA receiver is not a limitation to these teachings; they may be employed in any diversity receiver such as may be operating in a UTRAN (universal mobile telecommunications terrestrial radio access network) system, or an E-UTRAN (evolved UTRAN) system, or a WLAN (wireless local area network) system, or a WCDMA (wireless code division multiple access) system, a cognitive radio system, and the like. Additionally, it will be apparent these teaching may be employed in any receiver operating in a multiple-input and multiple-output system.
  • UTRAN universal mobile telecommunications terrestrial radio access network
  • E-UTRAN evolved UTRAN
  • WLAN wireless local area network
  • WCDMA wireless code division multiple access
  • the type 3 HSDPA receiver typically applies the LMMSE method for the equalizer.
  • F and L define the equalizer filter length and the channel impulse response length in samples, respectively.
  • F + L consisting of the n th and 2 onwards transmitted chips.
  • T e C F defines the received signal vector of the / th receive branch consisting of successive F samples which depend on the n th and onwards transmitted chips.
  • the LMMSE based estimate for the Dth delayed transmitted composite chip S[)? - D] in s[n] is expressed as w LMMSE HH H + where ⁇ D stands for the unit vector whose the D + 1 th element is 1 , and other elements are all zeros.
  • the LMMSE estimates needs the information about the channel impulse responses (CIRs) and noise variances with respect to two receive antennas.
  • CIRs channel impulse responses
  • Conventional approaches to processing diversity signals on different branches assumes that the noise variance on both branches is equal (in a HSDPA type 3 receiver, this is reflected as assuming the common pilot channel (CPICH) power is one).
  • CPICH common pilot channel
  • the LMMSE solution for the type 3 receiver also needs the noise variance estimates and pilot power to transmitted signal power ratio Ec/lor ( ⁇ p ) estimate.
  • Equation [5] it is not necessary to explicitly estimate the pilot Ec/lor and noise variance for the LMMSE solution. Instead, a single diagonal loading factor K needs to be determined. Ideally, K can be obtained by calculating the product of ⁇ p and ⁇ ⁇ 2 . In practice, some suboptimal solutions are usually utilized to provide ⁇ . For instance, the signal to noise ratio (SNR) for the CPICH is measured at the output of the equalizer or the de-spreader, which is then used to adjust the diagonal loading factor to maximize the SNR of the signal being measured.
  • SNR signal to noise ratio
  • equation [5] can be formulated as:
  • ⁇ LMMSE (HH H + ⁇ - / 2f ) "1 H ⁇ 5 1 ,
  • exemplary embodiments of an LMMSE solution which accommodates for different noise variances are described.
  • the exemplary embodiments presented herein estimate the noise variances for two receive branches.
  • the LMMSE solution of those exemplary and non-limiting embodiments have similar complexity as equation [7] by virtue of the estimated noise variances.
  • exemplary embodiments presented herein estimate the noise variance ⁇ ⁇ and pilot power to total transmitted signal power ratio (Ec/lor, designated as ⁇ p ), which are then used for example in the HSDPA type 3 receiver.
  • Exemplary embodiments of this invention utilize the autocorrelation and cross- correlation coefficients of the received signals from two receive branches, and the channel impulse response (CIR) estimates h from the CPICH channel to estimate the noise variances ⁇ ⁇ 2 of two receive branches and pilot power to the total transmitted signal power ratio (Ec/lor, ⁇ p ).
  • the CIR is estimated by correlating the received signal with the training sequence transmitted in the common pilot channel (e.g., CPICH in HSDPA). We assume the CPICH has a nominal power (one), then correlate the received signal with the CPICH of different delays in terms of different samples of the received signal in order to estimate the channel coefficients (taps) corresponding to the different multipaths in the resolution of samples.
  • C 11 and C 22 refer to the autocorrelation coefficients of the received signal at the 1 st and 2 nd receive branches, respectively; and
  • C 12 defines the cross-correlation coefficient between the received signals at those two branches.
  • Single numerical subscripts refer to a particular (first, second) receive branch.
  • a receiver according to these teachings may have two or three or more diversity branches, and the pair-wise diversity processing may be done on any pair or on multiple pairs of those receive diversity branches.
  • a receiver with three diversity branches may process according to the below examples on branch 1 and 2, and also on branch 2 and 3, and then process the two results as another pair of diversity branches for combining and eventual output as the estimate of the received signal.
  • Equation [9] Re-arranging terms of equation [9] shows that the pilot power to the total transmitted signal power ratio (Ec/lor or ⁇ p ) and noise variances ⁇ ⁇ 2 can be estimated as:
  • the pilot power ratio Ec/lor and noise variances can be estimated as follows:
  • k + stands for the minimum of the noise variance in the system. This minimum may be set as a design factor in a practical receiver, and in the simulations detailed below it is set to 0.1.
  • equation [7] is then changed to
  • the example detailed above can be extended to the case where more than 2 receive antennas are used in the user equipment (UE). If a higher computation complexity is allowed in the UE, for instance, the UE is able to estimate the covahance matrix of the receive signals from two receiver antennas, that is, the autocorrelation and cross-correlation functions of the received signals are available in the UE.
  • the pilot Ec/lor and noise variances can be estimated according to known methods or methods yet to be developed.
  • FIG. 1 shows an exemplary embodiment of a diversity receiver 100, which in an exemplary embodiment is a type 3 receiver.
  • a wireless signal r(n) is received as a first diversity signal on a first (/ h ) diversity branch 110 having a first diversity antenna 112 and first branch receiver front end 114 [e.g., amplifier, demodulator, sampler, etc. to take the first diversity signal to baseband, which baseband first diversity signal is represented as r- ⁇ (n)].
  • the wireless signal r(n) is also received as a second diversity signal on a second (/ h ) diversity branch 120 having a second receive antenna 122 and second branch receiver front end 124 [e.g., similar amplifier, demodulator, sampler, etc. to take the second diversity signal to baseband, which baseband second diversity signal is represented as r 2 (n)].
  • an estimate of the channel impulse response (CIR) U 1 of the channel over which a first pilot signal was received (which is the same channel over which the baseband first diversity signal r- ⁇ (n) was received) is estimated at a first channel estimation block 116.
  • This first-branch CIR estimate U 1 is then output to both a noise variance and pilot power ratio block 130, and to a tap solver block 140.
  • the pilot signals are received on the CPICH which is transmitted from the transmitter's antenna.
  • the CPICH is transmitted at the same time as other data channels that are processed on the diversity branches, but the CPICH uses a different spreading code than the data channels.
  • the CPICH is therefore considered a superimposed training sequence, and so is considered herein as the 'same' channel as the data.
  • both branches use the CPICH to correlate the respective received signal to obtain the CIR estimate. It is noted that this correlation based CIR estimation method is also typical in downlink for the WCDMA system where the superimposed training signal is used.
  • time multiplexed training signal for example GSM (global system for mobile communications), CDMA2000 (code division multiple access 2000) and TD-SCDMA (time division-synchronous code division multiple access), would typically employ a more complex method such as for example a least squares algorithm to find the CIR estimate.
  • GSM global system for mobile communications
  • CDMA2000 code division multiple access 2000
  • TD-SCDMA time division-synchronous code division multiple access
  • an estimate of the channel impulse response (CIR) li 2 of the channel over which a second pilot signal was received (which is the same channel over which the baseband second diversity signal r 2 (n) was received) is estimated at a second channel estimation block 126.
  • the second CIR h 2 is output to both the noise variance and pilot power ratio block 130 and towards the tap solver block 140.
  • Figure 1 illustrates a parallel implementation 116, 126 to better keep up with real time processing in demanding high-throughput environments.
  • correlation estimator 150 receives from the baseband first diversity signal r- ⁇ (n) and second diversity signal r 2 (n) there is computed at a correlation estimator 150 correlation coefficients C 1 1 , which is an estimate from the baseband signals on the / h (first) and / h (second) diversity branches. Equation [9] above is one way in which the correlation estimator may compute the correlation coefficients Ci 2 , Cu and C 22 - These are also input to the noise variance and pilot power ratio block 130.
  • the noise variance and pilot power ratio block then has three separate inputs: the three correlation coefficients from the correlation estimation block; the first channel impulse response U 1 ; and the second channel impulse response (CIR) h 2 . From these are computed the three values shown at equation [10-a]: the estimated pilot channel power to total transmitted signal power ratio ⁇ p ; the noise variance ⁇ for the signal received on the first diversity branch 110; and the noise variance ⁇ ⁇ 2 2 for the signal received on the second diversity branch 120.
  • the minimum noise variance k + in the system may be retrieved from a local memory, for example after being hard-coded or signaled from the network.
  • noise variance scaling factor is used to scale the second channel impulse response h 2 at a first multiplier 129a; and to scale the baseband second diversity signal r 2 (n) at a second multiplier 129b.
  • the outputs of the tap solver block 140 which may be computed according to equation [13] above, are used to set the filter coefficients of a first finite impulse response (FIR) filter 118 along the first diversity branch 110, and to set the filter coefficients of a second finite impulse response (FIR) filter 128 along the first diversity branch 110.
  • the filtered baseband signals diversity signals r- ⁇ (n) and r 2 (n) are finally combined at a combiner 160 so as to finally output the estimate for the Dth delayed transmitted composite chip s[)? -Z)] according to equation [14] above.
  • the noise variance and pilot power ratio estimation block 130 provides the
  • the correlation estimation block 150 in Figure 1 estimates the correlation coefficients using the received signals, which in some exemplary embodiments may have a somewhat higher complexity than prior art approaches to receive diversity.
  • the signal processing technique detailed herein can be implemented in different embodiments as hardware, as software, or as a combination of hardware and software.
  • a wireless network 1 is adapted for communication over a wireless link 11 with an apparatus, such as a mobile communication device which may be referred to as a UE 10, via a network access node 12, such as a base station (e.g., Node B or e-Node B).
  • a network access node 12 such as a base station (e.g., Node B or e-Node B).
  • the network 1 may include a higher node 14 which is a controller of a radio network, known in various systems as a radio network controller RNC, network control element (NCE), mobility management entity (MME) or serving gateway (SGW).
  • RNC radio network controller
  • NCE network control element
  • MME mobility management entity
  • SGW serving gateway
  • the UE 10 includes a controller, such as a computer or a data processor (DP) 10A, a computer-readable memory medium embodied as a memory (MEM) 10B that stores a program of computer instructions (PROG) 10C, and a suitable radio frequency (RF) transceiver 10D for bidirectional wireless communications with the access node 12 via one or more antennas (112, 122 in Figure 1 ; or 36 in Figure 2B).
  • a controller such as a computer or a data processor (DP) 10A
  • a computer-readable memory medium embodied as a memory (MEM) 10B that stores a program of computer instructions (PROG) 10C
  • PROG program of computer instructions
  • RF radio frequency
  • the access node 12 also includes a controller, such as a computer or a data processor (DP) 12A, a computer-readable memory medium embodied as a memory (MEM) 12B that stores a program of computer instructions (PROG) 12C, and a suitable RF transceiver 12D for communication with the UE 10 via one or more antennas.
  • the access node 12 is coupled via a data / control path 13 to the higher node 14.
  • the access node 12 may also be coupled to another access node via a data / control path 15, or in other systems all communications between adjacent access nodes may run through the higher node 14.
  • the higher node 14 includes a controller, such as a computer or a data processor (DP) 14A, a computer-readable memory medium embodied as a memory (MEM) 14B that stores a program of computer instructions (PROG) 14C, and a modem (not shown) for communication with the access node 12 over the data/control path 13.
  • the higher node 14 may also interface the access node to other networks such as for example a publicly switched telephone network or the Internet.
  • the access node 12 also has a receiver and can implement these teachings for processing received signals on diversity branches, such as was detailed at Figure 1 for example.
  • the PROGs 10C and 12C is assumed to include program instructions that, when executed by the associated DP, enable the device to operate in accordance with the exemplary embodiments of the invention. That is, the exemplary embodiments of this invention may be implemented at least in part by computer software executable by the DP 10A of the UE 10 and/or by the DP 12A of the eNB 12, or by hardware, or by a combination of software and hardware (and firmware).
  • the UE 10 may be assumed to also include a noise variance and pilot SNR estimation block 10E, and the access node 12 may include a noise variance and pilot SNR estimation block 12E.
  • the various embodiments of the UE 10 can include, but are not limited to, cellular telephones, personal digital assistants (PDAs) having wireless communication capabilities, portable computers having wireless communication capabilities, image capture devices such as digital cameras having wireless communication capabilities, gaming devices having wireless communication capabilities, music storage and playback appliances having wireless communication capabilities, Internet appliances permitting wireless Internet access and browsing, as well as portable units or terminals that incorporate combinations of such functions.
  • PDAs personal digital assistants
  • portable computers having wireless communication capabilities
  • image capture devices such as digital cameras having wireless communication capabilities
  • gaming devices having wireless communication capabilities
  • music storage and playback appliances having wireless communication capabilities
  • Internet appliances permitting wireless Internet access and browsing, as well as portable units or terminals that incorporate combinations of such functions.
  • the computer readable MEMs 10B and 12B may be of any type suitable to the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor based memory devices, flash memory, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory.
  • the DPs 10A and 12A may be of any type suitable to the local technical environment, and may include one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on a multicore processor architecture, as non-limiting examples.
  • Figure 2B illustrates further detail of an exemplary UE in both plan view (left) and sectional view (right), and the invention may be embodied in one or some combination of those more function-specific components.
  • the UE 10 has a graphical display interface 20 and a user interface 22 illustrated as a keypad but understood as also encompassing touch-screen technology at the graphical display interface 20 and voice-recognition technology received at the microphone 24.
  • a power actuator 26 controls the device being turned on and off by the user.
  • the exemplary UE 10 may have a camera 28 which is shown as being forward facing (e.g., for video calls) but may alternatively or additionally be rearward facing (e.g., for capturing images and video for local storage).
  • the camera 28 is controlled by a shutter actuator 30 and optionally by a zoom actuator 32 which may alternatively function as a volume adjustment for the speaker(s) 34 when the camera 28 is not in an active mode.
  • a shutter actuator 30 and optionally by a zoom actuator 32 which may alternatively function as a volume adjustment for the speaker(s) 34 when the camera 28 is not in an active mode.
  • multiple transmit/receive antennas 36 that are typically used for cellular communication.
  • the antennas 36 may be multi-band for use with other radios in the UE.
  • the operable ground plane for the antennas 36 is shown by shading as spanning the entire space enclosed by the UE housing though in some embodiments the ground plane may be limited to a smaller area, such as disposed on a printed wiring board on which the power chip 38 is formed.
  • the power chip 38 controls power amplification on the channels being transmitted and/or across the antennas that transmit simultaneously where spatial diversity is used, and amplifies the received signals.
  • the power chip 38 outputs the amplified received signal to the radio-frequency (RF) chip 40 which demodulates and downconverts the signal for baseband processing.
  • the baseband (BB) chip 42 detects the signal which is then converted to a bit-stream and finally decoded. Similar processing occurs in reverse for signals generated in the apparatus 10 and transmitted from it.
  • Signals to and from the camera 28 pass through an image/video processor 44 which encodes and decodes the various image frames.
  • a separate audio processor 46 may also be present controlling signals to and from the speakers 34 and the microphone 24.
  • the graphical display interface 20 is refreshed from a frame memory 48 as controlled by a user interface chip 50 which may process signals to and from the display interface 20 and/or additionally process user inputs from the keypad 22 and elsewhere.
  • Certain embodiments of the UE 10 may also include one or more secondary radios such as a wireless local area network radio WLAN 37 and a Bluetooth® radio (BT) 39, which may incorporate an antenna on-chip or be coupled to an off-chip antenna.
  • secondary radios such as a wireless local area network radio WLAN 37 and a Bluetooth® radio (BT) 39, which may incorporate an antenna on-chip or be coupled to an off-chip antenna.
  • BT Bluetooth® radio
  • memories such as random access memory RAM 43, read only memory ROM 45, and in some embodiments removable memory such as the illustrated memory card 47 on which the various programs 10C are stored. All of these components within the UE 10 are normally powered by a portable power supply such as a battery 49.
  • the aforesaid processors 38, 40, 42, 44, 46, 50 may operate in a slave relationship to the main processor 10A, 12A, which may then be in a master relationship to them.
  • the noise variance and pilot power ratio block 130 (also shown as 10E for the UE and 12E for the access node) is embodied within the baseband chip 42, though it is noted that other embodiments need not be disposed there but may be disposed across various chips and memories as shown or disposed within another processor that combines some of the functions described above for Figure 2B. Any or all of these various processors of Fig.
  • 2B access one or more of the various memories, which may be on-chip with the processor or separate therefrom. Similar function-specific components that are directed toward communications over a network broader than a piconet (e.g., components 36, 38, 40, 42-45 and 47) may also be disposed in exemplary embodiments of the access node 12, which may have an array of tower-mounted antennas rather than the two shown at Fig. 2B.
  • Similar function-specific components that are directed toward communications over a network broader than a piconet e.g., components 36, 38, 40, 42-45 and 47
  • the access node 12 may have an array of tower-mounted antennas rather than the two shown at Fig. 2B.
  • Specific embodiments of the access node 12 may reflect in part the various chips and memories shown at Figure 2B for the UE 10.
  • PB3 which is the ITU (International Telecommunications Union) Pedestrian B channel with mobile speed of 3 km/hr (see table B.1 B at page 149 of 3GPP TS
  • Figure 3 compares throughput of a HSDPA type 3 receiver using the arrangement of Figure 1 against a similar HSDPA type 3 receiver which processes the diversity branches under the assumption of the same SNR, with a 10- dB gain on the first diversity receive branch and a 1 dB gain on the second diversity receive branch.
  • Figure 4 is similar but where the gain on the second diversity branch is 7 dB; and
  • Figure 5 charts throughput data for the condition that both branches have the same 10 dB gain.
  • Figures 3-5 the technique described herein is shown by Figures 3-5 to increase throughput (as compared to the case where the same SNR is assumed) under each of those plotted conditions, it can be seen that greater throughput improvement is achieved for greater differences in gain among the two diversity signals. It is noted that these simulation results are for the gains stipulated and for the specific embodiment of figure 1 compared to a conventional type 3 diversity receiver set forth at 3GPP TS25.101 ; other embodiments and other gain factors may show different results.
  • those actions comprise: determining noise variance for a signal on a first diversity branch of a receiver (block 610); determining noise variance for a signal on a second diversity branch of a receiver (block 612); scaling the signal on the second diversity branch as a function of a ratio of the first noise variance and the second noise variance (block 614); and estimating a received signal by combining the signal on the first diversity branch with the scaled signal on the second diversity branch (block 616, which may also include outputting the estimated received signal).
  • a first autocorrelation coefficient is computed from the signal on the first diversity branch and a second autocorrelation coefficient is computed from the signal on the second diversity branch and a cross correlation coefficient is computed from both of those signals (block 602). These three correlation coefficients are then used to determine the two noise variances of the above paragraph.
  • a first channel impulse response for the channel over which the first signal was received is estimated from a pilot signal
  • a second channel impulse response for the channel over which the second signal was received is estimated from a pilot signal (block 604).
  • the noise variances are determined using these channel impulse response estimates.
  • a ratio of pilot channel power to total signal power (block 606), where the pilot channel power is for the channel over which the pilot signals were received and total signal power is for the signal being estimated.
  • that power ratio is used to set coefficients for a first filter for filtering the signal on the first diversity branch and to set coefficients for a second filter for filtering the scaled signal on the second diversity branch (block 608) before they are combined into the estimated signal.
  • such an apparatus includes first determining means for determining noise variance for a signal on a first diversity branch (e.g. the noise variance estimation function at block 130 of Figure 1 ); second determining means for determining noise variance for a signal on a second diversity branch of a receiver (e.g.
  • scaling means for scaling the signal on the second diversity branch as a function of a ratio of the first noise variance and the second noise variance e.g., the second multiplier 129b at Figure 1
  • estimating means for estimating a received signal by combining the signal on the first diversity branch with the scaled signal on the second diversity branch e.g., the combiner 160 at Figure 1 .
  • FIG. 6 The various blocks shown in Figure 6 may be viewed as method steps, and/or as operations that result from operation of computer program code, and/or as a plurality of coupled logic circuit elements constructed to carry out the associated function(s). As noted above for the case where these teachings are applied to more than two diversity branches in a receiver, the extension of Figure 6 is straightforward as detailed above for the example of a three diversity branch receiver.
  • the various exemplary embodiments may be implemented in hardware or special purpose circuits, software, logic or any combination thereof.
  • some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device, although the invention is not limited thereto.
  • firmware or software which may be executed by a controller, microprocessor or other computing device, although the invention is not limited thereto.
  • various aspects of the exemplary embodiments of this invention may be illustrated and described as block diagrams, flow charts, or using some other pictorial representation, it is well understood that these blocks, apparatus, systems, techniques or methods described herein may be implemented in, as nonlimiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.
  • the integrated circuit, or circuits may comprise circuitry (as well as possibly firmware) for embodying at least one or more of a data processor or data processors, a digital signal processor or processors, baseband circuitry and radio frequency circuitry that are configurable so as to operate in accordance with the exemplary embodiments of this invention.
  • UTRAN universal mobile telecommunications system terrestrial radio access network
  • E-UTRAN evolved UTRAN or long term evolution LTE of UTRAN
  • WCDMA wideband code division multiple access
  • WLAN wireless local area network
  • GSM global system for mobile communications
  • connection means any connection or coupling, either direct or indirect, between two or more elements, and may encompass the presence of one or more intermediate elements between two elements that are “connected” or “coupled” together.
  • the coupling or connection between the elements can be physical, logical, or a combination thereof.
  • two elements may be considered to be “connected” or “coupled” together by the use of one or more wires, cables and/or printed electrical connections, as well as by the use of electromagnetic energy, such as electromagnetic energy having wavelengths in the radio frequency region, the microwave region and the optical (both visible and invisible) region, as several non- limiting and non-exhaustive examples.

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Abstract

Selon l'invention, une première variance de bruit est déterminée pour un signal reçu sur une première branche de diversité d'un récepteur, et une seconde variance de bruit est déterminée pour un signal reçu sur une seconde branche de diversité du récepteur. Le signal reçu sur la seconde branche de diversité est pondéré en fonction d'un rapport de la première variance de bruit et de la seconde variance de bruit. Un signal reçu est ensuite estimé en combinant le signal sur la première branche de diversité avec le signal pondéré sur la seconde branche de diversité. De cette manière, une complexité raisonnable est utilisée, pour traiter des signaux de diversité, qui exploite la différence de variance de bruit au niveau des différentes branches de diversité de réception, sans requérir une inversion matricielle et sans avoir à supposer la même variance de bruit parmi les branches de réception en diversité. Des procédés, des appareils et des programmes informatiques qui peuvent fonctionner dans un système HSDPA et d'autres systèmes sont également décrits.
PCT/FI2009/051014 2008-12-22 2009-12-18 Estimation de variance de bruit pour réception en diversité Ceased WO2010072893A1 (fr)

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